Xylem and phloem Flashcards
What does xylem tissue do?
Transports water and mineral ions UPWARDS.
made up of dead cells ( no cytoplasm)
- supported by lignin so it doesn’t collapse
What does phloem do?
Transports sugars both UP and DOWN
What is the vascular system made up of?
Xylem and phloem
on a stem cross section diagram ( the one with horizontal bars) is the “xylem” on the inside or outside?
INSIDE
what is the advantage of no “end walls” on a xylem?
Water can pass through easier.
Does the amount of lignin increase or decrease as the cell gets older?
The amount of lignin increases
Why are there “pits” in the xylem
So water and ions can move out of the vessels
What 4 things is phloem tissue made up of?
1) phloem fibres
2) Phloem parenchyma
3) companion cells
4) sieve tube elements
What do sieve tube elements do?
They allow solutes to pass through the sieves
which are the holes on the sieve plate
Do sieve tubes have a nucleus?
NO
they have few organelles
and a thin layer of cytoplasm
What do companion cells do?
They basically carry out the living functions for both themselves and the sieve tube elements.
E.g. they provide the energy required for the active transport of solutes.
Dissecting plant stem practical?
1) Use a scalpel to cut a thin cross section of the stem
2) Using tweezers place the cut section in water until they are to be used. (stops them from drying out)
3) Transfer the cut section into a dish containing a stain (E.g. TBO toluidine blue O)
4) Rinse of the cut section in water and mount it onto a slide.
What does TBO stain and what colour?
Stains the lignin walls blue- green
What is one way to improve the stem dissection practical?
Use can use different stains to highlight different parts of the cells.
